Recently, Croma Pharma has introduced chitosan-N-acetylcysteine eye drops, designed for treatment of symptoms related to DES. Chemically, chitosan is a polycationic biopolymer with favourable biological properties such as high biocompatibility and low toxicity. Additionally, the new formulation comprises N-acetylcysteine, which has been used in ophthalmology because of its mucolytic properties for several years. Based on theoretical considerations, one can hypothesize that the new chitosan derivative may show an increased adhesion to mucins of the ocular surface and may therefore be particularly beneficial in reducing the symptoms associated with DES. We have recently shown in a phase I trial that single instillation of chitosan-N-acetylcysteine eye drops is well tolerated in young healthy subjects.